With an ever-increasing number of applications of a computer system it is advantageous or even necessary to communicate certain contents to the user. In the case of a timetable-information-system for example the computer-system should be able to show the desired timetable-information as text to the user. The text should contain not only the departure times, for example, but should provide the user with all essential information in the form of complete sentences or other textual expressions. This information can be shown on a screen in writing or can be output acoustically by way of a corresponding natural language output over a loudspeaker.
The production of text, especially the generation of sentences through a computer system is known.
Thus it is possible, that certain whole sentences are stored in a memory of the computer system, so that they can be called up again by individual programs and displayed. For example the sentence “File not found.” can be stored and called up again at the appropriate time. Such procedures for the generation of sentences are also known as “canned text systems”. This procedure is obviously not useable for a large number of sentences or for generating a variable sentence.
It is also possible, that only part of a certain sentence, which is variably completed on its retrieval from the computer system, is stored in the memory. For example, the sentence “the desired telephone number is - . . . ” can be stored in the memory of the computer-system. On its retrieval, the computer system can add in the relevant telephone number and can output the complete sentence to the user. Such a system for the sentence generation is also known as a “template system”. While it undoubtedly allows a certain variable sentence generation, it is nevertheless still very restricted in its flexibility.
Finally it is possible, with help of knowledge-based linguistic systems, to generate diverse sentences variably through a computer system. With it, so-called semantic representations which, for example, contain the information to be given to the user are determined by the computer system in a non-sentence-bound and non-grammatical format. This must be changed by the computer system into textual expressions or complete sentences. Such systems for the generation of textual expressions from semantic representations necessitate a substantial expenditure in storage area, computing time and development activity, so that they have so far only been available for certain, narrowly restricted generation tasks.